Degradation of dyes using hydrodynamic cavitation: Process overview and cost estimation

Abstract

Greener technologies with high efficiency and cost-effectiveness are highly in need to degrade and mineralize the recalcitrant contaminants in water. Hydrodynamic Cavitation (HC) which is generated by pressure and velocity variation in the system has gained attention in wastewater treatment due to its scalability, high energy efficiency, minimized toxic solvent usage and simpler reactor design. Despite having multiple advantages over conventional biological oxidation, industrial-scale usage of HC has not gained enough popularity due to its relatively higher cost than existing processes. This review paper focuses on the application of hydrodynamic cavitation in dye treatment and provides an overview of studies on dye degradation using hydrodynamic cavitation alone or in combination with other oxidation processes. The effects of different operational, geometric, and physicochemical properties of solutions on the process performance have been analyzed and optimum values of different parameters for the treatment of different dyes have been mentioned. Different combinative approaches (HC/Ozone, HC/Fenton’s reagent, HC/Photocatalysis, HC/Hydrogen Peroxide) have also been discussed and comparative studies among them have been performed. Future directions have been addressed to carefully control the drawbacks associated with the processes. Detailed cost estimation and trade-off analysis for mineralization of dyes using HC at industrial scale operation has been performed and feasibility of performing HC in large scale has been confirmed where data (reaction rate constant, cavitation number, optimum pressure) available from lab scale analysis are taken as basis for scaling up. Overall, hydrodynamic cavitation offers promise for industrial application especially compared to the more traditionally applied ultrasound-based treatments.